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Re: Extreme slowness with xfs [WAS: Re: Slowness with new pc]

To: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>
Subject: Re: Extreme slowness with xfs [WAS: Re: Slowness with new pc]
From: Michael Tokarev <mjt@xxxxxxxxxx>
Date: Tue, 25 Nov 2008 21:39:38 +0300
Cc: Eric Sandeen <sandeen@xxxxxxxxxxx>, Stian Jordet <liste@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, Alan Piszcz <ap@xxxxxxxxxxxxx>
In-reply-to: <alpine.DEB.1.10.0811250456010.16346@xxxxxxxxxxxxxxxx>
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Justin Piszcz wrote:
[]
> barriers enabled:
> real    2m40.643s
> barriers disabled:
> real    0m27.612s

Barriers enabled:

$ time sh -c "tar xf linux-2.6.27.tar.bz2; sync"
real    2m3.317s
user    0m33.990s
sys     0m3.980s

$ time sh -c "rm -rf linux-2.6.27; sync"
real    1m4.033s
user    0m0.080s
sys     0m2.860s


Barriers disabled:

$ time sh -c "tar xf linux-2.6.27.tar.bz2; sync"
real    0m36.279s
user    0m25.610s
sys     0m2.800s

$ time sh -c "rm -rf linux-2.6.27; sync"
real    0m3.694s
user    0m0.010s
sys     0m2.230s


During unpack, with barriers=on, the cpu usage stays
hardy noticeable, while with barriers=off, the thing
becomes CPU-bound (needed for bzip2).

For comparison, here are results for jfs on the
same drive:

$ time sh -c "tar xf /stage/build/kernel/linux-2.6.27.tar.bz2; sync"
real    0m36.062s
user    0m25.370s
sys     0m2.860s

$ time sh -c "rm -rf linux-2.6.27; sync"
real    0m3.024s
user    0m0.040s
sys     0m0.750s

This jfs partition is located a bit further on the same disk,
so raw speed of it is a bit lower.  Yet the numbers are pretty
similar.  In any case, xfs with barriers is MUCH worse...

The disk is a 500Gig Hitachi HUA72105 one ("raid edition"),
on an AMD 780g/SB700 chipset in ahci mode.

/mjt

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